The purpose of this project is to examine longitudinal measures of height and weight on 1144 cystic fibrosis patients seen at Rainbow Babies and Childrens Hospitial (RB&C) in Cleveland, Ohio. Growth curves will be fit to each individual's data and the parameters of those curves will be compared to parameters generated from an Ohio sample of healthy children (the Fels Longitudinal Growth Study in Yellow Springs). This comparison will reveal at what ages growth is most retarded in CF patients, and whether growth deficits result from a steady decline or from specific periods of subnormal growth. The relative contributions of proposed determinants of growth retardation in CF will be assessed by using measures of pancreatic enzyme secretion (serum carotene and immunoreactive trypsin levels), longitudinal pulmonary function test results, and chronic lung infection history from microbiology cultures as predictors of growth status. In addition to standard multiple regression techniques, a comprehensive explanatory path model for growth retardation in CF incorporating these variables will be developed and tested. The effects of improved medical treatments for CF will be examined through analysis of growth trends over the last 30 years of treatment at RB&C. Finally, the hypothesis that variability in growth status, pancreatic and pulmonary function, and clinical course results from genetic heterogeneity (due to multiple alleles at the CF locus or to background genetic variation), will be tested by comparing height and weight percentiles for age, pancreatic function, and pulmonary involvement within and among sibships of CF patients. This research will increase understanding of the relationship between the basic CF defect, its two major clinical symptoms (maldigestion and chronic lung disease), and delayed growth, and may contribute to our ability to ameliorate growth retardation in CF patients.